1. Field of the Invention
The present invention relates to a plug inner frame with twisted blades to reduce the manufacture cost.
2. Description of the Related Art
A plug is a necessary element to all kinds of computers, electric appliances, etc and thus plays an important role in daily life. A typical plug generally comprises two or three blades or prongs manufacture, a wire is attached to an end of each blade, and the blades are then embedded into an inner frame. The semi-product comprised of the wires and the blades embedded in the inner frame is then placed into a mold for subsequent injection molding to form the final plug with a housing.
Most advanced countries require each blade of the plug to be partially wrapped by an insulating layer at an exposed section thereof, thereby avoiding electric shocks in case that the plug is loosened. The insulating layer is generally made of plastic material and wraps a portion of the exposed section of the blade by means of injection molding. However, the insulating layer is apt to be disengaged from the smooth metal surface of the blade as a result of poor bonding force therebetween. Thus, the insulating layer would slide easily, and sometimes may even fall. The blade is then exposed again and thus could cause an electric shock.
FIG. 1 of the drawings illustrates a conventional plug blade 1 including an enclosed section 11 and an exposed section 12. The exposed section 12 includes a wider front section 121 and a narrower rear section 122 having a transverse through-hole 123. Plastic material is filled to a face of the narrower rear section 122 and flows through the transverse through-hole 123 to the other face of the narrower rear section 122. An insulating layer is formed on the narrower rear section 122 after hardening of the plastic material. The bonding force between the insulating layer and the narrower rear section 122 is improved, and the time for filling the plastic material is reduced. FIG. 2 shows another conventional plug blade 1 that is substantially identical to that of the plug blade 1 in FIG. 1, except that the upper and lower faces of the narrower rear section 122 are respectively flush with those of the wider front section 121.
However, an end of a wire must be inserted into and thus embraced by an end of each blade of the plug before subsequent procedure. The blades must face the same direction when proceeding with this wire-inserting procedure in an associated wire-inserting machine. In some countries, the blades of a plug are twisted such that the wire-inserting grooves of the blades face different directions. The current wire-inserting machine could not proceed with the wire-inserting procedure on the plugs with twisted blades. The manufacture cost is largely increased when seeking a solution to this end. In addition, a fault (generally a shallow recess) is formed on a surface of the insulating layer after hardening of the plastic material. The appearance of the plug is thus adversely affected.